#include <stdio.h>

int f1(int (*f)(int));
int f2(int i);

int main(void) {
  printf("Answer: %d\n", f1(f2));
  return 0;
}

int f1(int (*f)(int)) {
  int n = 0;

  while ((*f)(n))
    n++;
  return n;
}

int f2(int i) { return i * i + i - 12; }